#10 – Why we use gas prices to teach unit conversions (and why you should too!)

Unit conversions is important to learn, but to teach unit conversions is boring because most examples are irrelevant to life. Sure, we can teach students to convert kilometres to millimetres (and that might be important for certain science applications). But, when is a student really ever going to need to know how far the distance between the sun and the earth is in centimetres? Or, how often does a person today need to determine the number of chickens required to buy 3 horses if one horse is worth 5 pigs which, in turn, are worth 7 chickens. Simply put, no one will ever need to use unit conversions in such a way. So, how can we teach unit conversions in a useful way that is relevant to students?


Using REAL life to Teach Unit Conversions

Early in my career, I used to teach unit conversions by getting students to determine the better deal between things sold at Costco and identical items sold at the regular supermarket. It worked alright, but not all students had Costco memberships so not all students could relate. Furthermore, if a student in my class came from a country without Costco, not only could they not relate but I would also have to spend extra time describing the magical place known as Costco (also known as Kirklandia, I think.).


Today, one activity I use to teach unit conversions incorporates 2 things all students from every country can relate with: money and gasoline. Basically, I get students to rank countries (from a set I determine beforehand) gas prices from cheapest to most expensive. The twist to this activity is that not all gas prices are stated in the same way in each country. Some countries state prices in dollars per gallon, while others state them in euros per litre. Even if 2 countries use dollars, dollars aren’t worth the same in both countries. For example, the US dollar is worth more than the Canadian dollar currently. Another good thing about this activity is that it requires students to perform 2 conversions instead of just 1. These conversions take place both for the denominator and numerator. With 10 countries on my gas price list, students get a lot of practice (and, for those who don’t get it, we get a lot of opportunity for discussion too).


We show you what we use to develop this activity so that you can develop your own. However, if you would like a copy of our activity (which has a list of countries using 2017 gas prices), you can click a link and enter your email below to get a copy.


Field Notes

  • Using GlobalPetrolPrices.com, I research the price of gas sold in different countries of the world in Canadian dollars (CAD) per litre. It’s in CAD/L because I’m Canadian and I teach Canadian students. Adjust this to the currency you prefer.
  • Using xe.com, I convert gas prices from Canadian dollars per litre to other countries’ currencies. Example, if the price of gas in the US is stated as 0.87 CAD/L, it changes to 0.70 USD/L. I also write down the exchange rate (currently 1 CAD = 0.806 USD) for later use.
  • Using Wikipedia (Gallon), I convert volumes from litres to gallons for countries that use gallons. Note: there are 2 types of gallons (Imperial and US). Wikipedia states which countries use Imperial gallons and which use US gallons. Thus, the price of gas in the US previously stated as 0.70 USD/L converts to 2.64 USD/gal. If Germany is one of my countries on my list, I don’t convert the volume because German gas prices are in Euros/litre.
  • I give the list of 10-12 countries with corresponding gas prices (stated in the way it would in their country) to students. They need to rank gas prices from cheapest to most expensive by first converting all prices to CAD/L.
  • It is quite arbitrary what units you want students to ultimately convert to as a base unit. I use CAD/L because I’m Canadian and I have Canadian students (not to mention I teach in Canada).
  • As an extension,  I get my students to write a CER (Claim Evidence Reasoning) statement regarding gas prices and countries after they write their rankings. If you don’t know what CER is, take a look at #4 – “Does Knuckle Cracking Lead to Arthritis?” 3 CER examples based on FUN Science and #9 – Does Aspartame help with weight loss? 3 CER practice activities from real science data.


Putting it all together

The key to making learning fun (and having it stick) is to make it relevant to students. That’s not a new concept – many have said that before me. Part of making it relevant is to work with something common to every student’s life. In the case of unit conversions, we use gas prices as the common experience. But, there are many different variations (ex. Milk or beef prices, video games or video game systems, price of magazines or books). The hard part is finding the common experience. Click the link below and enter your email address to join our email list and to get a copy of our activity.


To Get Our Gas Price Conversions Activity, Click Here


Until next time, keep it REAL.

Posted on September 8, 2017 in Activities

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